Nearly 20 years after an earlier proposed merger was rejected by U.S. regulators, Staples says it is acquiring Office Depot for $6.3 billion. Combined, the two office supply giants would have annual sales of some $39 billion.

"Staples began discussions to acquire Office Depot in September 2014," the companies said in a news release. "The agreement has been unanimously approved by each company's Board of Directors."

The deal calls for Office Depot shareholders to be paid $7.25 in cash for each share of stock; they would also receive 0.2188 of a share in Staples stock. Staples says that at a total value of around $11 a share, the offer represents a 44 percent premium over Office Depot's recent closing price.

It's not certain whether the two retailers will be allowed to merge. The last time they tried, the Federal Trade Commission voted 4-1 against it, back in September 1996. The companies challenged the ruling in court but lost the case.

The purchase of Office Depot follows its own 2013 acquisition of OfficeMax, a merger that left it with annual sales of $17 billion, with some 66,000 employees and 2,200 stores worldwide.

At the time of that acquisition, Staples reportedly controlled about 40 percent of the U.S. office supply market, with the other two companies accounting for a total of about 35 percent of the U.S. market.

Copyright 2016 NPR. To see more, visit